The present invention relates to wear disks for crimping machines for manufacturing synthetic fibers.
Such wear disks, which are to prevent the sideways escape of the tow from the nip of the stuffer box, are known; their requirements have been discussed at great length for example in DE-A-2 113 886.
According to said reference, wear disks must be highly heat conductive, since in crimping, in particular dry crimping, the moving fiber bundles create friction which is converted into heat. To perform their function, wear disks must be in frictional contact with the end surfaces of the intake rolls, and the fiber plugs stuffed in the crimping box are moved along them under high pressure. In this process, the frictional area of the disks, i.e. a relatively small portion of their surfaces, additionally develops a great deal of heat. The material of the wear disks must therefore be highly heat conductive to ensure rapid dissipation of the heat generated and to prevent a fiber-damaging increase in the temperature of the friction surface. The high level of friction also leads to rapid wear of the disks, which is why it is an advantage to use a very abrasion-resistant material to make these parts. Abrasion-resistant, hard materials which have been proposed for the manufacture of wear disks are for example brass or ceramics (U.S. Pat. No. 4,395,804) or alumina mixed ceramics, e.g. (R) ALSIMAG (U.S. Pat. No. 2,311,174). The conventional materials which have this property, for example sinter ceramics formed from alumina or zirconia/silica, however, are not sufficiently heat conductive. A further disadvantage of these very hard materials is that any isolated instances of damage to the frictional surfaces of rotating disks are no longer repaired (worn away) in use and that the end surfaces of the intake rolls may be damaged.
Examples of softer materials recommended for wear disks are bronze, aluminum, nylon and PTFE (DE-A-3 503 447, DE-A-2 604 505, U.S. Pat. No. 3,237,270 and DE-A-1 435 441) and even graphite (DE-A-2 113 886). A problem with the current wear disks made of graphite is not only their high rate of wear but also their staining of the filaments, which is highly undesirable.
It is true that the widely used brass wear disks are highly heat conductive, but they still do not have a sufficiently long life or adequate self-repair properties. Plastics disks possess inadequate thermal conductivity.